Solar cell and method for manufacturing the same

ABSTRACT

A solar cell and a method for manufacturing the solar cell are discussed. The method for manufacturing the solar cell includes applying an electrode paste on a semiconductor substrate and sintering the electrode paste using a light sintering device to form an electrode. The electrode paste includes fine metal particles, a binder, and a solvent. An amount of the fine metal particles is greater than a sum of an amount of the binder and an amount of the solvent, and the amount of the binder is greater than the amount of the solvent.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2015-0108565, filed in the Korean IntellectualProperty Office on Jul. 31, 2015, the entire content of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

Embodiments of the invention relate to a solar cell and a method formanufacturing the same.

Description of the Related Art

In an industrial field including semiconductors, displays, solar cells,light emitting diodes (LEDs), etc., which are in the leading edge ofmodern technology industry, a very fine electronic pattern is formed onthe surface of a glass substrate or a silicon substrate, and variousfunctions of the industrial field are implemented using the electronicpattern.

However, a need to form the electronic pattern on a polymer or plasticsubstrate or paper, that are light and flexible, without forming theelectronic pattern on the hard and heavy glass substrate has beenrecently on the rise strongly in the industrial field. Various attemptshave been made to achieve the need.

As a method for forming the electronic pattern on the flexible substrateor the paper, a method has been proposed to form the electronic patternon the substrate through a printing method and then to sinter theelectronic pattern. It has been proposed to use white light in applyingthe method to a large-area substrate while sintering the electronicpattern at a low temperature.

It has been proposed to use a white light irradiation device in atechnology for irradiating the white light onto an object and rapidlyand accurately drying the object. Thus, the development of the whitelight irradiation device, that is usable in various fields, has beenrequired.

SUMMARY OF THE INVENTION

In one aspect, there is provided a method for manufacturing a solar cellincluding applying an electrode paste on a semiconductor substrate andsintering the electrode paste using a light sintering device to form anelectrode, wherein the sintering of the electrode paste includes a firstevaporation operation for evaporating a solvent included in theelectrode paste, a second evaporation operation for irradiating pulsetype white light to evaporate a binder included in the electrode paste,and sintering fine metal particles to form the electrode.

It is preferable, but not required, that the pulse type white light isgenerated through a xenon flash lamp.

The electrode paste may include fine metal particles, a binder, and asolvent. An amount of the fine metal particles may be greater than a sumof an amount of the binder and an amount of the solvent, and the amountof the binder may be greater than the amount of the solvent. The finemetal particles may include at least one conductive material of silver(Ag), copper (Cu), Cu—Ni or Cu—Ag.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 illustrates an example of a solar cell according to an exampleembodiment of the invention;

FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1;

FIGS. 3A and 3B illustrate configuration of a light sintering device;

FIG. 4 is a graph illustrating parameters used in irradiation conditionsof pulse type white light generated in a lamp;

FIGS. 5A to 5C sequentially illustrate a method for manufacturing asolar cell shown in FIGS. 1 and 2;

FIGS. 6A to 6D sequentially illustrate a light sintering method using alight sintering device shown in FIGS. 3A and 3B;

FIG. 7 illustrates another example of a back surface field region shownin FIGS. 1 and 2; and

FIGS. 8 to 10 illustrate other examples of a solar cell according to anexample embodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to embodiments of the invention,examples of which are illustrated in the accompanying drawings. Thisinvention may, however, be embodied in many different forms and shouldnot be construed as limited to the embodiments set forth herein.Wherever possible, the same reference numbers will be used throughoutthe drawings to refer to the same or like parts. It will be noted that adetailed description of known arts will be omitted if it is determinedthat the detailed description of the known arts can obscure theembodiments of the invention.

In the drawings, the thickness of layers, films, panels, regions, etc.,are exaggerated for clarity. It will be understood that when an elementsuch as a layer, film, region, or substrate is referred to as being “on”another element, it can be directly on the other element or interveningelements may also be present. In contrast, when an element is referredto as being “directly on” another element, there are no interveningelements present. Further, it will be understood that when an elementsuch as a layer, film, region, or substrate is referred to as being“entirely” on other element, it may be on the entire surface of theother element and may not be on a portion of an edge of the otherelement.

In the following description, “front surface” may be one surface of asemiconductor substrate, on which light is directly incident, and “backsurface” may be a surface opposite the one surface of the semiconductorsubstrate, on which light is not directly incident or reflective lightmay be incident.

In the following description, the fact that any two values aresubstantially equal to each other means that the two values are equal toeach other within a margin of error of 10% or less.

A solar cell according to an embodiment of the invention is describedwith reference to FIGS. 1 to 10.

FIG. 1 illustrates an example of a solar cell according to an exampleembodiment of the invention. FIG. 2 is a cross-sectional view takenalong line A-A of FIG. 1.

As shown in FIGS. 1 and 2, a solar cell 10 according to an exampleembodiment of the invention may include a semiconductor substrate 110,an emitter region 120, a first anti-reflection layer 130, a plurality offirst electrodes 140, a back surface field (BSF) region 170, a secondanti-reflection layer 132, and a plurality of second electrodes 150.

The solar cell 10 according to the embodiment of the invention is abifacial solar cell that receives light from the outside through a firstsurface and a second surface of the semiconductor substrate 110, and canproduce electric current using light incident on the first surface andthe second surface of the semiconductor substrate 110.

The first and second anti-reflection layers 130 and 132 and the backsurface field region 170 may be omitted, if necessary or desired. In thefollowing description, the embodiment of the invention describes thesolar cell including the first and second anti-reflection layers 130 and132 and the back surface field region 170 as an example because thefirst and second anti-reflection layers 130 and 132 and the back surfacefield region 170 further improve efficiency of the solar cell.

The semiconductor substrate 110 includes the first surface (hereinafter,referred to as “front surface”) and the second surface (hereinafter,referred to as “back surface”), and the front surface and the backsurface are positioned opposite each other.

The semiconductor substrate 110 may be formed of silicon of a firstconductive type, for example, an n-type, though not required. Siliconused in the semiconductor substrate 110 may be single crystal silicon,polycrystalline silicon, or amorphous silicon. For example, thesemiconductor substrate 110 may be formed of a crystalline siliconwafer.

When the semiconductor substrate 110 is of the n-type, the semiconductorsubstrate 110 may be doped with impurities of a group V element, such asphosphorus (P), arsenic (As), and antimony (Sb). Alternatively, thesemiconductor substrate 110 may be of a p-type. If the semiconductorsubstrate 110 is of the p-type, the semiconductor substrate 110 may bedoped with impurities of a group III element, such as boron (B), gallium(Ga), and indium (In).

At least one of the front surface and the back surface of thesemiconductor substrate 110 may have a plurality of uneven portions, soas to increase an absorptance of light by reducing a reflectance oflight at the front surface and the back surface of the semiconductorsubstrate 110. FIGS. 1 and 2 show that only an edge of the semiconductorsubstrate 110 has the uneven portions for the sake of brevity and easeof reading. Thus, FIGS. 1 and 2 show that only an edge of the emitterregion 120 positioned on the front surface of the semiconductorsubstrate 110 has the uneven portions. However, in fact, the entirefront surface of the semiconductor substrate 110 has the unevenportions, and the entire surface of the emitter region 120 positioned onthe front surface of the semiconductor substrate 110 has the unevenportions.

Light incident on the front surface of the semiconductor substrate 110having the plurality of uneven portions is reflected several times bythe uneven portions of the emitter region 120 and the uneven portions ofthe semiconductor substrate 110 and is incident inside the semiconductorsubstrate 110. Hence, an amount of light reflected from the frontsurface of the semiconductor substrate 110 decreases, and an amount oflight incident inside the semiconductor substrate 110 increases.Further, surface areas of the semiconductor substrate 110 and theemitter region 120, on which light is incident, increase by the unevenportions, and an amount of light incident on the semiconductor substrate110 increases.

As shown in FIGS. 1 and 2, the emitter region 120 is formed at the frontsurface of the semiconductor substrate 110 of the first conductive typeand is a region formed by doping the semiconductor substrate 110 withimpurities of a second conductive type (for example, p-type) oppositethe first conductive type (for example, n-type). Namely, the emitterregion 120 may be positioned inside the front surface of thesemiconductor substrate 110. Thus, the emitter region 120 of the secondconductive type forms a p-n junction along with a first conductive typeregion of the semiconductor substrate 110.

Carriers, i.e., electron-hole pairs produced by light incident on thesemiconductor substrate 110 are separated into electrons and holes bythe p-n junction between the semiconductor substrate 110 and the emitterregion 120. Then, the separated electrons may move to the n-typesemiconductor, and the separated holes may move to the p-typesemiconductor. Thus, when the semiconductor substrate 110 is of then-type and the emitter region 120 is of the p-type, the separatedelectrons may move to the semiconductor substrate 110, and the separatedholes may move to the emitter region 120.

Because the emitter region 120 forms the p-n junction along with thesemiconductor substrate 110, i.e., the first conductive type region ofthe semiconductor substrate 110, the emitter region 120 may be of then-type when the semiconductor substrate 110 is of the p-type unlike theembodiment described above. In this instance, the separated holes maymove to the back surface of the semiconductor substrate 110, and theseparated electrons may move to the emitter region 120.

Returning to the embodiment of the invention, when the emitter region120 is of the p-type, the emitter region 120 may be formed by doping thesemiconductor substrate 110 with impurities of a group III element, suchas B, Ga, and In. On the contrary, when the emitter region 120 is of then-type, the emitter region 120 may be formed by doping the semiconductorsubstrate 110 with impurities of a group V element, such as P, As, andSb.

As shown in FIGS. 1 and 2, the first anti-reflection layer 130 ispositioned on the front surface of the semiconductor substrate 110. Whenthe emitter region 120 is positioned on the front surface of thesemiconductor substrate 110, the first anti-reflection layer 130 may bepositioned on the emitter region 120.

The first anti-reflection layer 130 may be formed of at least one ofaluminum oxide (AlOx), silicon nitride (SiNx), silicon oxide (SiOx), andsilicon oxynitride (SiOxNy).

The first anti-reflection layer 130 reduces a reflectance of lightincident on the solar cell 10 and increases selectivity of apredetermined wavelength band, thereby increasing the efficiency of thesolar cell 10.

When the semiconductor substrate 110 has the uneven portions, the firstanti-reflection layer 130 includes an uneven surface having a pluralityof uneven portions similar to the semiconductor substrate 110.

In the embodiment of the invention, the first anti-reflection layer 130has a single-layered structure. However, the first anti-reflection layer130 may have a multi-layered structure, for example, a double-layeredstructure. In this instance, a passivation function of the firstanti-reflection layer 130 may be further strengthened, and photoelectricefficiency of the solar cell 10 may be further improved. The firstanti-reflection layer 130 may be omitted, if necessary or desired.

The first anti-reflection layer 130 may be formed on the front surfaceof the semiconductor substrate 110 using a chemical vapor deposition(CVD) method, such as a plasma enhanced chemical vapor deposition(PECVD) method.

As shown in FIGS. 1 and 2, the back surface field region 170 may bepositioned at the back surface opposite the front surface of thesemiconductor substrate 110. The back surface field region 170 is aregion (for example, an n⁺-type region) which is more heavily doped thanthe semiconductor substrate 110 with impurities of the same conductivetype as the semiconductor substrate 110.

A potential barrier is formed by a difference between impurityconcentrations of the first conductive type region of the semiconductorsubstrate 110 and the back surface field region 170. The potentialbarrier prevents or reduces holes from moving to the back surface fieldregion 170 used as a moving path of electrons and makes it easier forelectrons to move to the back surface field region 170. Thus, the backsurface field region 170 reduces an amount of carriers lost by arecombination and/or a disappearance of electrons and holes at andaround the back surface of the semiconductor substrate 110 andaccelerates a movement of desired carriers (for example, electrons),thereby increasing the movement of carriers to the second electrodes150.

As shown in FIGS. 1 and 2, the second anti-reflection layer 132 may bepositioned on the back surface opposite the front surface of thesemiconductor substrate 110. When the back surface field region 170 ispositioned at the back surface of the semiconductor substrate 110, thesecond anti-reflection layer 132 may be positioned on the back surfacefield region 170. In this instance, the second anti-reflection layer 132may minimize the reflection of light incident on the back surface of thesemiconductor substrate 110.

The second anti-reflection layer 132 may be formed of at least one ofaluminum oxide (AlOx), silicon nitride (SiNx), silicon oxide (SiOx), andsilicon oxynitride (SiOxNy). The first anti-reflection layer 130 and thesecond anti-reflection layer 132 may be formed of the same material ordifferent materials.

Further, the first anti-reflection layer 130 and the secondanti-reflection layer 132 may be formed using the same method ordifferent methods.

A passivation layer may be formed between the first anti-reflectionlayer 130 and the emitter region 120 and between the secondanti-reflection layer 132 and the back surface field region 170. Thepassivation layer may be formed of non-crystalline semiconductor. Forexample, the passivation layer may be formed of intrinsic hydrogenatedamorphous silicon (i-a-Si:H). The passivation layer may perform apassivation function, which converts a defect, for example, danglingbonds existing at and around the surface of the semiconductor substrate110 into stable bonds using hydrogen (H) contained in the passivationlayer and prevents or reduces a recombination and/or a disappearance ofcarriers moving to the surface of the semiconductor substrate 110. Thus,the passivation layer may reduce an amount of carriers lost by thedefect at and around the surface of the semiconductor substrate 110.Hence, the passivation layer positioned on the front surface and theback surface of the semiconductor substrate 110 may reduce an amount ofcarriers lost by the defect at and around the surface of thesemiconductor substrate 110, thereby improving the efficiency of thesolar cell.

As shown in FIGS. 1 and 2, the plurality of first electrodes 140 arepositioned on the front surface of the semiconductor substrate 110 andare separated from one another. Each first electrode 140 may extend in afirst direction x. The electrodes, which are separated from one anotheron the front surface of the semiconductor substrate 110 and extend inthe first direction x, may be referred to as front fingers.

The plurality of first electrodes 140 may pass through the firstanti-reflection layer 130 and may be electrically and physicallyconnected to the emitter region 120 positioned at the front surface ofthe semiconductor substrate 110. Namely, the first electrodes 140 may bepositioned on the emitter region 120, on which the first anti-reflectionlayer 130 is not positioned.

The plurality of first electrodes 140 may be formed of at least oneconductive material, for example, copper (Cu) and may collect carriers(for example, holes) moving to the emitter region 120.

As shown in FIGS. 1 and 2, the plurality of second electrodes 150 arepositioned on the back surface of the semiconductor substrate 110 andare separated from one another. Each second electrode 150 may extend inthe first direction x. The electrodes, which are separated from oneanother on the back surface of the semiconductor substrate 110 andextend in the first direction x, may be referred to as back fingers. Thesecond electrodes 150 may be positioned opposite the first electrodes140 at a location corresponding to the first electrodes 140 with thesemiconductor substrate 110 interposed therebetween. Hence, the numberof second electrodes 150 may be the same as the number of firstelectrodes 140. The embodiment of the invention is not limited thereto.

The plurality of second electrodes 150 may pass through the secondanti-reflection layer 132 and may be electrically and physicallyconnected to the back surface field region 170 positioned at the backsurface of the semiconductor substrate 110. Namely, the secondelectrodes 150 may be positioned on the back surface field region 170,on which the second anti-reflection layer 132 is not positioned.

The plurality of second electrodes 150 may be formed of at least oneconductive material, for example, cooper (Cu) and may collect carriers(for example, electrons) moving to the back surface field region 170.

In the bifacial solar cell, because an amount of light incident on thefront surface of the semiconductor substrate 110 is more than an amountof light incident on the back surface of the semiconductor substrate110, the number of second electrodes formed on the back surface of thesemiconductor substrate 110 may be more than the number of firstelectrodes formed on the front surface of the semiconductor substrate110. In this instance, a distance (i.e., a pitch) between the secondelectrodes 150 may be less than a distance between the first electrodes140.

FIGS. 3A and 3B illustrate configuration of a light sintering device.FIG. 4 is a graph illustrating parameters used in irradiation conditionsof pulse type white light generated in a lamp.

The first electrodes 140 and the second electrodes 150 according to theembodiment of the invention may be formed using a light sintering device20.

As shown in FIGS. 3A and 3B, the light sintering device 20 may include alight output unit 200, a power supply unit, a capacitor, and a transferunit 220.

The light output unit 200 may include a lamp 201, a reflective plate202, a light wavelength filter 203, a light induction unit 204, and acooling unit 205.

The light output unit 200 may be positioned on the transfer unit 220.The light output unit 200 may receive a voltage and a current from thepower supply unit and may receive carriers accumulated in the capacitor,thereby producing arc plasma. Hence, the light output unit 200 mayoutput pulse type white light to the surface of the semiconductorsubstrate 110 and sinter an electrode paste through the irradiation ofthe pulse type white light, thereby forming an electrode.

As shown in FIG. 3B, the lamp 201 may use a xenon flash lamp. It ispreferable, but not required, that white light is irradiated in asurface form.

The xenon flash lamp includes a xenon gas injected into a sealed quartztube of a cylinder shape. The xenon gas outputs light energy fromreceived electrical energy and has an energy conversion percentageexceeding 50%. Further, the xenon flash lamp includes a metal electrode,for example, a tungsten electrode in order to form an anode electrodeand a cathode electrode on both sides of the xenon flash lamp. When thepower supply unit applies high power and high current to the lamp 201,the xenon gas injected into the inside of the lamp 201 is ionized, and aspark is generated between the anode electrode and the cathodeelectrode. In this instance, when carriers accumulated in the capacitorare applied to the lamp 201, an arc plasma and light of a strongintensity are generated inside the lamp 201 while a current of about1,000 A flows for 1 ms to 10 ms through the spark generated inside thelamp 201. The generated light has a light spectrum from ultravioletlight to infrared light, that are distributed in a wide wavelength of160 nm to 2.5 mm, and thus is seen as white light.

The embodiment of the invention is described using the xenon flash lampas an example of the lamp 201. Other lamps may be used as long as theabove-described object can be achieved.

As shown in FIG. 4, the irradiation conditions using the lamp 201 may becontrolled by parameters including an energy E, a pulse width W, anumber N of pulses (hereinafter referred to as “pulse-number”), and apulse gap G of the lamp 201 irradiating light, etc. It is preferable,but not required, that the lamp 201 uses the xenon flash lamp.

In the embodiment of the invention, the energy E of the lamp 201 may beabout 1 J/cm² to 100 J/cm², more preferably, about 1 J/cm² to 50 J/cm².

When the energy E of the lamp 201 is less than about 1 J/cm², anelectrode paste may not be smoothly sintered. When the energy E of thelamp 201 exceeds about 100 J/cm², the light sintering device 20 may beoverloaded.

It is preferable, but not required, that the pulse width W of the lamp201 is 0.1 ms to 50 ms in consideration of efficiency of a sinteringprocess. More preferably, the pulse width W of the lamp 201 may be 0.1ms to 20 ms.

It is preferable, but not required, that the number N of pulses of thelamp 201 is one to one hundred in consideration of the efficiency of thesintering process. More preferably, the number N of pulses may be one tofifty.

When the number N of pulses of the lamp 201 is equal to or greater thanthree, it is preferable, but not required, that a pulse gap of the xenonflash lamp is 1 ms to 100 ms in consideration of the efficiency of thesintering process and an influence on a lifespan of the light sinteringdevice 20. More preferably, the pulse gap of the xenon flash lamp may be5 ms to 50 ms.

As shown in FIG. 3B, the reflective plate 202 is positioned on an upperpart of the lamp 201 and may change a light path so that pulse typewhite light output from the lamp 201 in the opposite direction of thesemiconductor substrate 110 is output in a direction of thesemiconductor substrate 110. Namely, the reflective plate 202 may causelight upwardly irradiated from the lamp 201 to be downwardly irradiatedfrom the lamp 201.

As shown in FIG. 3B, the light wavelength filter 203 is positioned on alower part of the lamp 201 and filters only intense pulsed white lighthaving a predetermined wavelength band. In particular, becauseultraviolet light irradiated from the lamp 201 using the xenon flashlamp may damage the semiconductor substrate 110 formed of a polymermaterial, light having an ultraviolet wavelength band has to be blocked.Further, a wavelength band of irradiated light may be selectivelyblocked depending on a kind of the semiconductor substrate 110.

As shown in FIG. 3B, the light induction unit 204 is positioned on alower part of the light wavelength filter 203 and may adjust a positionof the pulse type white light so that the pulse type white light may beirradiated onto the semiconductor substrate 110.

As shown in FIG. 3B, the cooling unit 205 may supply a coolant to thelamp 202 through a cooling path in order to reduce a surface temperatureof the lamp 201. Because the surface temperature of the lamp 201 mayrises to about 1200K to 1500K during a light output, an overheatingphenomenon of the light output unit 200 can be prevented by cooling thelamp 201.

The power supply unit may generate a voltage and a current and maytransfer the generated voltage and current to the light output unit 200.

The capacitor may accumulate and store carriers. When a spark isgenerated between both electrodes of the lamp 201 of the light outputunit 200, the capacitor may transfer the stored carriers to the lamp201.

As shown in FIG. 3B, the transfer unit 220 is positioned on a lower partof the light output unit 200. The transfer unit 220 may be a convey belt(or a conveyor belt) and may transfer the semiconductor substrate 110 inone direction. In this instance, the transfer unit 220 may include aheating plate for heating the semiconductor substrate 110 or a coolingplate for cooling the semiconductor substrate 110.

When the semiconductor substrate 110 is additionally heated through theheating plate, the sintering may be performed by a small energy ofintense pulsed white light. Further, a lifespan of the lamp 201 mayincrease. When the semiconductor substrate 110 is additionally cooledthrough the cooling plate, damage of the semiconductor substrate 110 maybe prevented.

In the bifacial solar cell having the above-described configuration,when light irradiated onto the solar cell 10 is incident on thesemiconductor substrate 110 through the emitter region 120 and the backsurface field region 170, a plurality of electron-hole pairs aregenerated in the semiconductor substrate 110 by light energy producedbased on the incident light. In this instance, because the front surfaceand the back surface of the semiconductor substrate 110 are the texturedsurface, a light reflectance at the front surface and the back surfaceof the semiconductor substrate 110 is reduced. Further, because bothincident and reflective operations are performed at the texturedsurfaces of the semiconductor substrate 110, the light is confined inthe solar cell 10. As a result, an absorptance of light increase, andthe efficiency of the bifacial solar cell, i.e., the solar cell 10, isimproved.

In addition, because a reflection loss of light incident on thesemiconductor substrate 110 is reduced by the first anti-reflectionlayer 130 and the second anti-reflection layer 132, an amount of lightincident on the semiconductor substrate 110 further increases.

The electron-hole pairs are separated into electrons and holes due tothe p-n junction between the semiconductor substrate 110 and the emitterregion 120. Then, the separated electrons move to the back surface ofthe n-type semiconductor substrate 110, and the separated holes move tothe p-type emitter region 120. In this instance, the semiconductorsubstrate 110 may be of the n-type and the emitter region 120 may be ofthe p-type.

The electrons moving to the semiconductor substrate 110 move to thesecond electrodes 150 through the back surface field region 170, and theholes moving to the emitter region 120 move to the first electrodes 140.When the first and second electrodes 140 and 150 are connected to eachother using electric wires, current flows therein to thereby enable useof the current for electric power.

FIGS. 5A to 5C sequentially illustrate a method for manufacturing asolar cell shown in FIGS. 1 and 2. FIGS. 6A to 6D sequentiallyillustrate a light sintering method using a light sintering device shownin FIGS. 3A and 3B.

A method for manufacturing the solar cell according to the embodiment ofthe invention is described below with reference to FIGS. 5A to 5C andFIGS. 6A to 6D.

The front surface and the back surface of the semiconductor substrate110 are formed as the textured surface. The emitter region 120 is formedat the front surface of the semiconductor substrate 110, and the backsurface field region 170 is formed at the back surface of thesemiconductor substrate 110.

More specifically, a high temperature thermal process of a material (forexample, B₂H₆) containing impurities of a group III element, such asboron (B), gallium (Ga), and indium (In), is performed on the n-typesemiconductor substrate 110 to diffuse the impurities of the group IIIelement into the semiconductor substrate 110. Hence, the p-type emitterregion 120 is formed at the entire surface of the semiconductorsubstrate 110.

If the semiconductor substrate 110 is of the p-type in anotherembodiment of the invention, a high temperature thermal process of amaterial (for example, POCl₃ or H₃PO₄) containing impurities of a groupV element, such as phosphorus (P), arsenic (As), and antimony (Sb), maybe performed on the semiconductor substrate 110 to diffuse theimpurities of the group V element into the semiconductor substrate 110.Hence, the n-type emitter region 120 may be formed at the entire surfaceof the semiconductor substrate 110.

Subsequently, phosphorous silicate glass (PSG) containing phosphor (P)or boron silicate glass (BSG) containing boron (B) produced when n-typeimpurities or p-type impurities are diffused into the semiconductorsubstrate 110 is removed through an etching process.

In this instance, each of the front surface and the back surface of thesemiconductor substrate 110 are formed as the textured surface using awet etching process or a dry etching process using plasma. Hence, theemitter region 120 has the uneven surface due to the shape of thetextured surface of the semiconductor substrate 110.

Next, the back surface field region 170 is formed at the back surface ofthe semiconductor substrate 110 using a thermal diffusion method.

More specifically, the thermal diffusion method may pre-deposit amaterial (for example, BBr₃) containing impurities of a group IIIelement, such as boron (B), gallium (Ga), and indium (In), on thesemiconductor substrate 110 and may drive-in the pre-depositedimpurities of the group III element into the semiconductor substrate 110to form the back surface field region 170.

The back surface field region 170 may be formed at the entire backsurface of the semiconductor substrate 110 as shown in FIGS. 1 and 2.Alternatively, the back surface field region 170 may be locally formedat a location corresponding to the second electrodes 150 at the backsurface of the semiconductor substrate 110.

For example, as shown in FIG. 7, the back surface field region 170 maybe locally formed at a location corresponding to the second electrodes150 at the back surface of the semiconductor substrate 110 by depositingand diffusing impurities of a group III element.

The emitter region 120 and the back surface field region 170 may beformed through a process using laser doping, a process using laserpatterning and laser doping, a process using an anti-diffusion layer,and the like.

Next, the first anti-reflection layer 130 and the second anti-reflectionlayer 132 are respectively formed on the front surface and the backsurface of the semiconductor substrate 110 using various layer formationmethods, for example, the PECVD method. The first anti-reflection layer130 and the second anti-reflection layer 132 may be formed of the samematerial or different materials. The first anti-reflection layer 130 andthe second anti-reflection layer 132 may have a single-layered structureor a multi-layered structure and may be formed using the same method ordifferent methods.

A passivation layer may be formed between the first anti-reflectionlayer 130 and the emitter region 120 and between the secondanti-reflection layer 132 and the back surface field region 170.

Next, the solar cell 10 including the first and second anti-reflectionlayers 130 and 132 on the front surface and the back surface of thesemiconductor substrate 110 is positioned on the transfer unit 220 ofthe light sintering device 20.

Next, as shown in FIG. 5A, a first electrode paste 140 a is applied tothe front surface of the semiconductor substrate 110 in the firstdirection x. In this instance, various application methods including aninkjet printing method, a screen printing method, a spin coating method,etc. may be used to apply the first electrode paste 140 a to the frontsurface of the semiconductor substrate 110.

More specifically, as shown in FIG. 6A, the first electrode paste 140 amay include fine metal particles 1, a binder 2, and a solvent 3. In thisinstance, the first electrode paste 140 a is in a non-sintered state.

The fine metal particles 1 may be formed of at least one conductivematerial of silver (Ag), copper (Cu), Cu—Ni or Cu—Ag and may be amicro-sized powder or a nano-sized powder.

The first electrode paste 140 a may include the fine metal particles 1of about 50 to 80 wt %, the binder 2 of about 15 to 40 wt %, and thesolvent 3 of about 5 to 40 wt %.

It is preferable, but not required, that an amount of the fine metalparticles 1 is greater than a sum of an amount of the binder 2 and anamount of the solvent 3, and the amount of the binder 2 is greater thanthe amount of the solvent 3.

Next, as shown in FIG. 5B, pulse type white light is irradiated onto thefront surface of the semiconductor substrate 110 to sinter the firstelectrode paste 140 a. Hence, the first electrode 140 is formed. In thisinstance, an evaporation of the solvent 3 and an evaporation of thebinder 2 of the first electrode paste 140 a are performed at a lowtemperature (for example, equal to or lower than 500° C.).

More specifically, as shown in FIG. 6B, the solvent 3 included in thefirst electrode paste 140 a is evaporated. In this instance, the solvent3 may be evaporated at a minimum temperature of about 80° C. Forexample, the solvent 3 may be evaporated at a temperature of about 80°C. to 150° C.

Next, as shown in FIG. 6C, pulse type white light is irradiated onto thefirst electrode paste 140 a, in which the solvent 3 is evaporated, toevaporate the binder 2. The temperature of the evaporation of the binder2 may be different from the temperature of the evaporation of thesolvent 3. For example, since the pulse type white light is irradiatedin the evaporation of the binder 2, the temperature of the evaporationof the binder 2 may be higher than the temperature of the evaporation ofthe solvent 3. In this instance, the binder 2 may be evaporated at atemperature equal to or higher than about 100° C. For example, thebinder 2 may be evaporated at a temperature of about 100° C. to 500° C.

However, the embodiment of the invention is not limited thereto. Thebinder 2 may be evaporated at the same temperature as the solvent 3.

An irradiation time of the pulse type white light (more specifically,irradiation time it takes to irradiate the pulse type white light once)may be about 0.1 ms to 10 ms and may be adjusted depending on theamounts of the fine metal particles 1, the binder 2, and the solvent 3included in the first electrode paste 140 a. For example, theirradiation time of the pulse type white light (more specifically, theirradiation time it takes to irradiate the pulse type white light once)may be about 0.1 ms to 2 ms, and the irradiation time it takes toirradiate the pulse type white light 10 to 30 times may be about 1 ms to40 ms. The sintering of the fine metal particles 1 may be efficientlyperformed within the above range.

Next, as shown in FIG. 6D, the first electrode 140 is formed bysintering the fine metal particles 1. In the embodiment of theinvention, the first electrode 140 may be formed of copper (Cu).

As described above, the light sintering device 20 may irradiate thepulse type white light generated from the xenon flash lamp onto thefirst electrode paste 140 a including the fine metal particles 1 andthus may sinter the fine metal particles 1 without damage.

Further, the light sintering device 20 may irradiate the pulse typewhite light onto the first electrode paste 140 a for about 0.1 ms to 10ms, thereby reducing time required in the sintering process.

The fine metal particles 1 formed of a material, for example, copper(Cu), that is easily oxidized, may be sintered for a short period oftime through a reduction in time required in the sintering process.Thus, the oxidization of the fine metal particles 1 can be prevented.

It is generally known that it is very difficult to sinter copper becausean oxide layer is formed on the surface of copper due to thermalchemical equilibrium, resulting in a reduction in conductivity of copperafter the sintering. Further, because a laser sintering method may beused to sinter a very small area, the laser sintering method lackspracticality.

However, because the embodiment of the invention irradiates the pulsetype white light onto the fine metal particles 1 for a short period oftime using the xenon flash lamp to sinter the fine metal particles 1,the oxidization of the fine metal particles 1 can be prevented.

Moreover, because the first electrode 140 is formed of copper, thematerial cost can be further reduced. Thus, the embodiment of theinvention can simplify the sintering process and reduce the materialcost without a reduction in an adhesive strength between thesemiconductor substrate 110 and the first electrode 140, thereby furtherimproving the efficiency of the solar cell.

Next, as shown in FIG. 5C, a second electrode paste 150 a is applied tothe back surface of the semiconductor substrate 110 at a locationcorresponding to the first electrode paste 140 a in the first directionx. The second electrode paste 150 a may be formed on the back surface ofthe semiconductor substrate 110 through the same method as the firstelectrode paste 140 a.

More specifically, as shown in FIG. 6A, the second electrode paste 150 amay include fine metal particles 1, a binder 2, and a solvent 3. In thisinstance, the second electrode paste 150 a is in a non-sintered state.

The fine metal particles 1 may be formed of at least one conductivematerial of silver (Ag), copper (Cu), Cu—Ni or Cu—Ag and may be amicro-sized powder or a nano-sized powder.

The second electrode paste 150 a may include the fine metal particles 1of about 50 to 80 wt %, the binder 2 of about 15 to 40 wt %, and thesolvent 3 of about 5 to 40 wt %.

It is preferable, but not required, that an amount of the fine metalparticles 1 is greater than a sum of an amount of the binder 2 and anamount of the solvent 3, and the amount of the binder 2 is greater thanthe amount of the solvent 3.

The second electrode paste 150 a may be formed using the same materialas the first electrode paste 140 a. Other materials may be used.

Next, as shown in FIG. 5C, pulse type white light is irradiated onto theback surface of the semiconductor substrate 110 to sinter the secondelectrode paste 150 a. Hence, the second electrode 150 is formed. Inthis instance, an evaporation of the solvent 3 and an evaporation of thebinder 2 of the second electrode paste 150 a are performed at a lowtemperature (for example, equal to or lower than 500° C.).

More specifically, as shown in FIG. 6B, the solvent 3 included in thesecond electrode paste 150 a is evaporated. In this instance, thesolvent 3 may be evaporated at a minimum temperature of about 80° C. Forexample, the solvent 3 may be evaporated at a temperature of about 80°C. to 150° C.

Next, as shown in FIG. 6C, pulse type white light is irradiated onto thesecond electrode paste 150 a, in which the solvent 3 is evaporated, toevaporate the binder 2. The temperature of the evaporation of the binder2 may be different from the temperature of the evaporation of thesolvent 3. For example, since the pulse type white light is irradiatedin the evaporation of the binder 2, the temperature of the evaporationof the binder 2 may be higher than the temperature of the evaporation ofthe solvent 3. In this instance, the binder 2 may be evaporated at atemperature equal to or higher than about 100° C. For example, thebinder 2 may be evaporated at a temperature of about 100° C. to 500° C.

However, the embodiment of the invention is not limited thereto. Thebinder 2 may be evaporated at the same temperature as the solvent 3.

An irradiation time of the pulse type white light may be about 0.1 ms to10 ms and may be adjusted depending on the amounts of the fine metalparticles 1, the binder 2, and the solvent 3 included in the secondelectrode paste 150 a.

Next, as shown in FIG. 6D, the second electrode 150 is formed bysintering the fine metal particles 1. In the embodiment of theinvention, the second electrode 150 may be formed of copper (Cu).

As described above, the light sintering device 20 may irradiate thepulse type white light generated from the xenon flash lamp onto thesecond electrode paste 150 a including the fine metal particles 1 andthus may sinter the fine metal particles 1 without damage.

Further, the light sintering device 20 may irradiate the pulse typewhite light onto the second electrode paste 150 a for about 0.1 ms to 10ms, thereby reducing time required in the sintering process.

The fine metal particles 1 formed of a material, for example, copper(Cu), that is easily oxidized, may be sintered for a short period oftime through a reduction in time required in the sintering process.Thus, the oxidization of the fine metal particles 1 can be prevented.

It is generally known that it is very difficult to sinter copper becausean oxide layer is formed on the surface of copper due to thermalchemical equilibrium, resulting in a reduction in conductivity of copperafter the sintering. Further, because a laser sintering method may beused to sinter a very small area, the laser sintering method lackspracticality.

However, because the embodiment of the invention irradiates the pulsetype white light onto the fine metal particles 1 for a short period oftime using the xenon flash lamp to sinter the fine metal particles 1,the oxidization of the fine metal particles 1 can be prevented.

Moreover, because the second electrode 150 is formed of copper, thematerial cost can be further reduced. Thus, the embodiment of theinvention can simplify the sintering process and reduce the materialcost without a reduction in an adhesive strength between thesemiconductor substrate 110 and the second electrode 150, therebyfurther improving the efficiency of the solar cell.

The embodiment of the invention described that the second electrode isformed after the first electrode is formed, but is not limited thereto.For example, the second electrode may be formed, and then the firstelectrode may be formed.

FIGS. 8 to 10 illustrate other examples of a solar cell according to anexample embodiment of the invention.

As shown in FIG. 8, another example of a solar cell according to theembodiment of the invention, to which the electrode forming methodaccording to the embodiment of the invention is applicable, may includefront fingers 141 extending in the first direction x and a front bus bar142 extending in a direction (i.e., a second direction y) crossing alongitudinal direction of the front fingers 141 as a first electrode140, unlike FIGS. 1 and 2.

A second electrode 150 may include back fingers 151, that are positionedon a back surface of a semiconductor substrate 110 to be separated fromone another and extend in the first direction x, and a back bus bar 152extending in a direction (i.e., the second direction y) crossing alongitudinal direction of the back fingers 151.

For example, the back fingers 151 may be formed at a locationcorresponding to the front fingers 141 of the first electrode 140, andthe back bus bar 152 may be formed at a location corresponding to thefront bus bar 142 of the first electrode 140.

Furthermore, as shown in FIG. 9, the electrode forming method accordingto the embodiment of the invention may be applied to a solar cell, inwhich first and second electrodes 140 and 150 are positioned on a backsurface of a semiconductor substrate 110.

More specifically, an emitter region 120 containing first impurities isformed at the back surface of the semiconductor substrate 110.

Next, a back surface field region 170 containing second impurities of aconductive type opposite the first impurities is formed at the backsurface of the semiconductor substrate 110 and is separated from theemitter region 120.

Next, a passivation layer 130 is formed on a front surface of thesemiconductor substrate 110 opposite the back surface of thesemiconductor substrate 110.

Next, a first electrode paste 140 a is applied to the emitter region120, and a second electrode paste 150 a is applied to the back surfacefield region 170 using various application methods including an inkjetprinting method, a screen printing method, a spin coating method, etc.Then, the first electrode 140 is formed on the emitter region 120, andthe second electrode 150 is formed on the back surface field region 170using the light sintering device 20. Namely, the light sintering device20 may irradiate the pulse type white light onto the back surface of thesemiconductor substrate 110 to sinter the first electrode paste 140 aand the second electrode paste 150 a. Hence, the first electrode 140connected to the emitter region 120 and the second electrode 150connected to the back surface field region 170 may be formed.

The first electrode paste 140 a may include fine metal particles 1 ofabout 50 to 80 wt %, a binder 2 of about 15 to 40 wt %, and a solvent 3of about 5 to 40 wt %. It may be preferable, but not required, that anamount of the fine metal particles 1 is greater than a sum of an amountof the binder 2 and an amount of the solvent 3, and the amount of thebinder 2 is greater than the amount of the solvent 3.

The second electrode paste 150 a may include fine metal particles 1 ofabout 50 to 80 wt %, a binder 2 of about 15 to 40 wt %, and a solvent 3of about 5 to 40 wt %. It may be preferable, but not required, that anamount of the fine metal particles 1 is greater than a sum of an amountof the binder 2 and an amount of the solvent 3, and the amount of thebinder 2 is greater than the amount of the solvent 3.

Furthermore, as shown in FIG. 10, the electrode forming method accordingto the embodiment of the invention may be applied to a solar cell, inwhich a first electrode 140 having a two-layered structure including afirst electrode layer 140L and a first transparent electrode layer 140Cand a second electrode 150 having a two-layered structure including asecond electrode layer 150L and a second transparent electrode layer150C are positioned on a back surface of a semiconductor substrate 110.

A solar cell shown in FIG. 10 may include a semiconductor substrate 110,a tunnel layer 180 on a back surface of the semiconductor substrate 110,a first conductive region (an emitter region) 120, a second conductiveregion (a back surface field region) 170, an insulating layer 190, afirst electrode 140, and a second electrode 150. In the embodimentdisclosed herein, the tunnel layer 180 may be omitted, if desired ornecessary. The embodiment of the invention is described using the solarcell including the tunnel layer 180 as an example.

A front surface of the semiconductor substrate 110 may be an unevensurface having a plurality of uneven portions or having unevencharacteristics. Hence, an amount of light reflected from the frontsurface of the semiconductor substrate 110 may decrease, and an amountof light incident on the inside of the semiconductor substrate 110 mayincrease.

The tunnel layer 180 may be formed between the entire back surface ofthe semiconductor substrate 110 and front surfaces of the first andsecond conductive regions 120 and 170. Thus, a front surface of thetunnel layer 180 may directly contact the entire back surface of thesemiconductor substrate 110, and a back surface of the tunnel layer 180may directly contact the front surfaces of the first and secondconductive regions 120 and 170. The tunnel layer 180 may be formed bydepositing a dielectric material or a semiconductor material on the backsurface of the semiconductor substrate 110. Namely, the tunnel layer 180may include a dielectric material or a semiconductor material.

More specifically, the tunnel layer 180 may be formed of the dielectricmaterial such as silicon oxide (SiOx) or the semiconductor material suchas amorphous silicon (a-Si) and silicon carbide (SiC). Other materialsmay be used. For example, the tunnel layer 180 may be formed of siliconnitride (SiNx), hydrogenated SiNx, aluminum oxide (AlOx), siliconoxynitride (SiON), or hydrogenated SiON.

Carriers produced in the semiconductor substrate 110 may pass throughthe tunnel layer 180, and the tunnel layer 180 may perform a passivationfunction with respect to the back surface of the semiconductor substrate110.

A thickness of the tunnel layer 180 may be 1 nm to 3 nm, so as toproperly perform the passivation function with respect to thesemiconductor substrate 110 while causing carriers produced in thesemiconductor substrate 110 to pass through the tunnel layer 180. Evenwhen a high temperature thermal process is used to manufacture the solarcell, the tunnel layer 180 may prevent or reduce characteristics (forexample, carrier life time) of the semiconductor substrate 110 frombeing damaged.

The first and second conductive regions 120 and 170 may be formed of asingle crystal silicon material, a polycrystalline silicon material, anamorphous silicon material, or a metal oxide material. In this instance,the first conductive region 120 and the second conductive region 170 maybe respectively doped with impurities of a first conductive type andimpurities of a second conductive type and may have opposite conductivetypes. Alternatively, when the first and second conductive regions 120and 170 are formed of the metal oxide material, the first and secondconductive regions 120 and 170 may have opposite conductive types byFermi level of the metal oxide material. At least one of the first andsecond conductive regions 120 and 170 may have a conductive typeopposite the semiconductor substrate 110 and function as an emitterregion, and the other may have the same conductive type as thesemiconductor substrate 110 and function as a back surface field region.

The insulating layer 190 may be positioned between the first and secondelectrodes 140 and 150 and on a portion, which is not connected to thefirst and second electrodes 140 and 150 in back surfaces of the firstand second conductive regions 120 and 170.

The insulating layer 190 between the first and second electrodes 140 and150 can prevent a short circuit between the first and second electrodes140 and 150. Further, the insulating layer 190 on the back surfaces ofthe first and second conductive regions 120 and 170 can perform apassivation function to remove a defect resulting from a dangling bondat the back surfaces of the first and second conductive regions 120 and170 and to prevent carriers produced in the semiconductor substrate 110from being recombined and disappeared by the dangling bond.

The insulating layer 190 may be formed of a dielectric material. Forexample, the insulating layer 190 may be formed of at least one ofamorphous silicon oxide (a-SiOx), amorphous silicon nitride (a-SiNx),amorphous silicon carbide (a-SiCx), or aluminum oxide (AlOx). Inaddition, the insulating layer 190 may be formed of at least one ofhydrogenated silicon nitride (SiNx:H), hydrogenated silicon oxide(SiOx:H), hydrogenated silicon nitride oxide (SiNxOy:H), hydrogenatedsilicon oxynitride (SiOxNy:H), or hydrogenated amorphous silicon(a-Si:H).

In the embodiment of the invention, the first and second electrodes 140and 150 may respectively include first and second electrode layers 140Land 150L which have a surface shape (or a planar shape) of a two-layeredstructure.

More specifically, the first electrode 140 may include the firstelectrode layer 140L which is entirely formed on the back surface of thesemiconductor substrate 110 in the surface shape and has an opening in aformation area of the second conductive region 170. Further, the secondelectrode 150 may include the second electrode layer 150L which isconnected to the second conductive region 170 through the opening of thefirst electrode layer 140L, is separated from the first electrode layer140L while overlapping the first electrode layer 140L at the backsurface of the semiconductor substrate 110, and is entirely formed onthe back surface of the semiconductor substrate 110 in the surfaceshape.

As described above, when the first and second electrodes 140 and 150 areconfigured as the two-layered structure of the first and secondelectrode layers 140L and 150L, a resistance loss of the first andsecond electrodes 140 and 150 can be minimized by minimizing ahorizontal movement distance of carriers. Further, a tabbing process forconnecting a plurality of solar cells in series using an interconnectorto modularize the plurality of solar cells may be further simplified.

The first electrode 140 may further include a first transparentelectrode layer 140C positioned between the first electrode layer 140Land the first conductive region 120. The first transparent electrodelayer 140C may be entirely formed on the back surface of thesemiconductor substrate 110 in the surface shape and may have aplurality of openings in a formation area of the second conductiveregion 170. The first transparent electrode layer 140C may be directlyconnected to the first conductive region 120.

Further, the second electrode 150 may further include a secondtransparent electrode layer 150C that is positioned in a formation areaof the openings of the first transparent electrode layer 140C and ispositioned between the second electrode layer 150L and the secondconductive region 170. The second transparent electrode layer 150C mayfunction to connect the second electrode layer 150L to the secondconductive region 170 through the first electrode layer 140L or theopenings of the first transparent electrode layer 140C.

The first and second transparent electrode layers 140C and 150C may beformed of transparent conductive oxide. For example, the first andsecond transparent electrode layers 140C and 150C may be formed of atleast one of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide(ZnO), indium tungsten oxide (IWO), or hydrogen-doped indium oxide(IO:H).

The first and second transparent electrode layers 140C and 150C canreduce contact resistances between the first and second transparentelectrode layers 140C and 150C and the first and second conductiveregions 120 and 170. Further, the first and second transparent electrodelayers 140C and 150C can prevent a plasma damage, an increase inrecombination of carriers, and diffusion of ions of a metal materialincluded in the first and second electrode layers 140L and 150L, whichmay be generated when the metal material included in the first andsecond electrode layers 140L and 150L is formed on the first and secondconductive regions 120 and 170, since the metal material, for example,copper (Cu) or aluminum (Al) included in the first and second electrodelayers 140L and 150L is not directly connected to the first and secondconductive regions 120 and 170 through the first and second transparentelectrode layers 140C and 150C.

After the first electrode paste 140 a or the second electrode paste 150a is applied, the first electrode paste 140 a or the second electrodepaste 150 a may be sintered using the light sintering device to form atleast one of the first and second electrode layers 140L and 150L. As anexample of forming the first and second electrode layers 140L and 150L,the first electrode layer 140L may be formed by applying the firstelectrode paste 140 a and then sintering the first electrode paste 140 ausing the light sintering device, and the second electrode layer 150Lmay be formed through a sputtering method, a printing method (forexample, a screen printing method), a deposition method, a platingmethod, and the like. As another example of forming the first and secondelectrode layers 140L and 150L, the first electrode layer 140L may beformed through the sputtering method, the printing method (for example,the screen printing method), the deposition method, the plating method,and the like, and the second electrode layer 150L may be formed byapplying the second electrode paste 150 a and then sintering the secondelectrode paste 150 a using the light sintering device. As anotherexample of forming the first and second electrode layers 140L and 150L,the first electrode layer 140L may be formed by applying the firstelectrode paste 140 a and then sintering the first electrode paste 140 ausing the light sintering device, and the second electrode layer 150Lmay be formed by applying the second electrode paste 150 a and thensintering the second electrode paste 150 a using the light sinteringdevice.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the scope of the principles of thisdisclosure. More particularly, various variations and modifications arepossible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A method for manufacturing a solar cell, themethod comprising: applying an electrode paste on a semiconductorsubstrate; and sintering the electrode paste using a light sinteringdevice to form an electrode.
 2. The method of claim 1, wherein theelectrode paste includes fine metal particles, a binder, and a solvent.3. The method of claim 2, wherein an amount of the fine metal particlesis greater than a sum of an amount of the binder and an amount of thesolvent, and the amount of the binder is greater than the amount of thesolvent.
 4. The method of claim 3, wherein the amount of the fine metalparticles is about 50 to 80 wt %.
 5. The method of claim 3, wherein theamount of the binder is about 15 to 40 wt %.
 6. The method of claim 3,wherein the amount of the solvent is about 5 to 40 wt %.
 7. The methodof claim 2, wherein the fine metal particles include at least oneconductive material of silver (Ag), copper (Cu), Cu—Ni or Cu—Ag.
 8. Themethod of claim 7, wherein the fine metal particles are a micro-sizedpowder or a nano-sized powder.
 9. The method of claim 2, wherein thesintering of the electrode paste includes: a first evaporation operationfor evaporating the solvent included in the electrode paste; a secondevaporation operation for irradiating pulse type white light toevaporate the binder included in the electrode paste; and sintering thefine metal particles to form the electrode.
 10. The method of claim 9,wherein the pulse type white light is generated through a xenon flashlamp.
 11. The method of claim 9, wherein the first and secondevaporation operations are performed at a temperature equal to or lowerthan 500° C.
 12. The method of claim 11, wherein the first and secondevaporation operations are performed at different temperatures.
 13. Themethod of claim 12, wherein the first evaporation operation is performedat a minimum temperature of about 80° C.
 14. The method of claim 12,wherein the second evaporation operation is performed at a temperatureequal to or higher than about 100° C.
 15. The method of claim 10,wherein an irradiation time of the xenon flash lamp is about 0.1 ms to10 ms.
 16. The method of claim 10, wherein energy of the xenon flashlamp is about 1 J/cm² to 100 J/cm².
 17. The method of claim 9, whereinthe electrode paste is applied using an inkjet printing method, a screenprinting method, or a spin coating method.
 18. The method of claim 9,wherein the light sintering device includes a light output unitoutputting the pulse type white light to the electrode paste andsintering the electrode paste through the irradiation of the pulse typewhite light.
 19. The method of claim 18, wherein the light output unitincludes: a reflective plate disposed on an upper part of a xenon flashlamp and changing a light path so that the pulse type white light outputfrom the xenon flash lamp in the opposite direction of the semiconductorsubstrate is output in a direction of the semiconductor substrate; alight wavelength filter disposed on a lower part of the xenon flash lampand filtering only the pulse type white light having a predeterminedwavelength band; a light induction unit disposed on a lower part of thelight wavelength filter and adjusting a position of the pulse type whitelight so that the pulse type white light is irradiated onto theelectrode paste; and a cooling unit supplying a coolant to the xenonflash lamp through a cooling path to cool the xenon flash lamp.
 20. Themethod of claim 18, wherein the light sintering device further includesa transfer unit disposed on a lower part of the light output unit andtransferring the semiconductor substrate in one direction.